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Rendering with Arnold in CINEMA 4D using the C4DtoA plug-in.
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C4DtoA Volumes

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pat.trudeau
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C4DtoA Volumes

I am having issues importing OpenVDB files into Arnold Volume in C4D. I followed the "writing volumes to VDB" tutorial, and I can see my .vdb file in Octane Volume, but in Arnold there is no bounding box and no visible VDB file. I thought it could be a scale issue but see no bounding box at any scale. I have tried the models featured on the OpenVDB.org downloads page, and most do not work, with the notable exception of Explosion.vdb and Fire.vdb. Even those behave differently than what I am told to expect when following Arnold volume tutorials. What am I doing wrong?

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I tested smoke1, smoke2 and the bunny_cloud from OpenVDB.org in C4DtoA 2.5.2.1 and they all work fine. It's probably just a scale issue, note that these volumes are in meter unit while the default scale of a C4D scene is cm, so you might need to change the Scale on the Arnold Volume to cm. Also note that the density and emission has to be scaled as well, so assign a standard_volume shader and increase the density to 100.

You can also check if the channels are displayed properly in the Available grids field of the Arnold Volume object and all grids (or at least the density) are exported.

Also you can check the console if there's any error in the log when you try to render the volume.

Message 3 of 3
pat.trudeau
in reply to: pat.trudeau

Thanks for your reply. You are correct about the scale, and I guess I was simply not increasing the density sufficiently. I am still having issues with my own Houdini .vdb exports however.

I also have a follow-up question. I am trying to follow this example:

https://docs.arnoldrenderer.com/display/AFCUG/Volume+Sample+RGB+Example?preview=/24119760/24085509/V...

but unable to replicate similar results with a standard volume shader as with the old volume collector. Can you tell me how to go about doing this? Thanks in advance.

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